BLACK  SANDS  FROM  PLACER  MINES. 
157 
In  undertaking  an  examination  of  these  specimens  it  was  evidently  necessary  to  define 
nore  or  less  generally  what  minerals  should  be  considered  "valuable."  More  than  fort} 
listinct  mineral  species  were  likely  to  be  encountered  in  one  or  another  of  those  sands, 
,nd  of  these  there  are  very  few  which  are  not  used  industrially  under  some  conditions  in 
ome  part  of  the  United  States.  The  first  essential  condition  determining  the  usefulness 
if  any  of  the  minerals  is  its  purity.  Therefore  the  ease  with  which  the  various  minerals 
ould  be  separated  became  an  important  feature  to  be  determined  by  the  investigation. 
It  was  important  to  determine  the  most  efficient  means  of  separating  the  various  minerals, 
s  an  aid  in  identifying  them,  in  determining  the  proportion  of  each  in  a  given  sample, 
,nd,  finally,  in  forming  a  satisfactory  conclusion  as  to  whether  the  conditions  involved  in 
eparation  would  admit  of  classifying  certain  minerals  as  useful. 
Prof.  Robert  H.  Richards,  dean  of  the  mining  school  of  the  Massachusetts  Institute  of 
echnology,  was  promptly  retained  to  carry  out  experiments  in  mineral  separation, 
ssisted  by  Mr.  F.  W.  Horton.  As  many  of  the  specimens  received  contained  noteworthy 
[uantities  of  gold  and  platinum,  they  were  first  assayed  by  Mr.  Charles  E.  Locke,  assistant 
o  Professor  Richards.  These  assays  showed  the  following  proportions  of  gold  to  platinum, 
mere  the  latter  element  was  detected: 
Jold  and  platinum  contained  in  black-sand  concentrates  from  various  placer-mining  districts, 
by  States  and  counties. 
lumber  of  sample. 
State  and  county. 
District. 
Ounces  per  ton 
of  concentrate. 
Gold. 
Plati- 
num. 
)  5007  No.  2 
)  5010 
ARIZONA. 
Columbia 
0.79 
Trace. 
Trace. 
19.94 
5.22 
1.09 
7.03 
.08 
39.08 
19.00 
Trace. 
5.60 
29.26 
24.14 
37.61 
191.60 
120.9 
1.45 
1.11 
10.80 
Trace. 
2.  98 
.12 
.64 
8.29 
.72 
0.06 
do   
Granite  Creek 
)  5008 
do 
Walnut  Grove 
).. 
CALIFORNIA. 
Butte... 
27.45 
)  8 
do 
Alvarado  placer  mine,  Butte  Creek 
Buchanan  Hill 
.17 
)  26 
.08 
)  29 
...do... 
.83 
)  30... 
.  do 
Trace. 
)  16 
Calaveras 
Humboldt 
Mendocino 
.35 
)  34 
Orleans 
4.00 
)  9 
Sec.  7,  T.  16  N.,  R.  12  W 
Trace. 
)  19 
.  52 
)2 
Taylor  mine,  North  Fork  American  River, 
Colfax. 
1.27 
)  1 
do   . 
1.48 
)  6 
.do 
Gold  Run 
8.78 
)  11 
do 
Gold  Blossom  mine,  Butcher  Ranch  min- 
ing district. 
3.36 
)  23 
...do 
'.1.67 
)  15 
.12 
)21 
do. 
Bowlder    Nest   mine    on    Grizzly    Creek, 
Genesee  district. 
.66 
)  32 
do 
.  16 
)  40 
....do   . 
Little  Grizzly  mine 
Trace. 
)  47  No.  1 
do 
21 
)  38 
San  Bernardino .  . 
.(H. 
p5 
Sacramento  River,  North  of  Redding,  Gem 
mine. 
Gypsy  mine,  Shasta  district 
.  28 
)  14 
do 
.25 
)18 
Siskiyou 
Fox  Creek 
Trace. 
